First I have to say that after having found OpenMW, I love it. From playing I found that the following would be great to add some quality of life enhancements for post 1.0. I only have basic coding experience so nowhere near where I could do these myself but figure at least maybe someone will be inspired to consider implementing them.

Reset actors command resetting moved npcs - I am unsure if this is the behavior in original Morrowind but if an actor moves as part of a question, using the reset actors command causes them to move to odd locations since sometime their cells have changed. I am assuming it moves them to the xyz positions they started in. For example, using ra in Ald-ruhn Temple after Ienas Sarandas moves there, causes him to move to an x,y,z position that puts him in the sky falling forever in the cell (specifically 3845.418945 4753.092773 13742.624023). If you use positioncell you can move him back but he'll die due to the fall. My suggestion is check if the cell the actor is different from where they were placed in the construction kit when the command runs, if it is, then the char is not reset. Or implement a new command resetactorsafe to have that check.

markposition, markpositioncell, recallposition, recallpositioncell console support - Implement a console command that marks the currently selected xyz coordinates and then moves them to a stored array. Effectively this makes one command to get xyz position and z rotation but also stores it to an array. So for example if you did player->markposition it would save their location. If you moved the player and then did player->recallposition it would move them back to the last spot markposition was run. The cell version does the same thing but uses position cell and remembers what cell the command was used in.

Resetinventory - resets a console selected inventory container to have stock item as if it did not have items placed in it. If used on a npc, it would reset their inventory to whatever base game/mods put on them.

qqq console support - I often find that I go into game and drop out often while making mods. It's something I got into the happen of doing in later ES games so would be nice.

Adding support for 'Themed Music' - Oblivion and on had specific music files for dungeons so that would be nice to have. I would like to see the OpenMW CS have support to choose what music folder plays for a cell. So for example, if you set a cell to play Dungeon music it looks in the Music folder for a folder called "Dungeons" and plays the music in there instead of explore. If possible, could this logic be implemented with the older cs kit by the engine looking for a unique activator (such as ac_omw_musicthemecrypt or ac_omw_musicthemedungeon) that if it is the current interior cell that it plays that music theme.

Occlusion Plane Support - While I think boundary boxes would take a lot of work, I think an occlusion plane that could be dropped in the OpenMW CS make help in densely populated areas where effectively objects behind it in view of the player would not be rendered. When I play Tamriel Rebuilt and visit Old Ebonheart it makes me think that this would be an area where it would be beneficial.

Adding a new AI for Companion/Follower or fixing existing follow AI - I know vanillaWind had lots of issues with npc followers getting stuck, perhaps if distance to PC gets too far behind they teleport a bit to get unstuck or if they are playing a walk animation and not changing position (which would suggest that they are stuck on an object that teleport kicks in). In addition, on using coc, fast travel, and Almsivi or Divine intervention, it would check if there is a current follower and bring them along with the traveling.

Adding bodypart types for accessories - specifically having an accessory slot 1,2,3 for modding. This would allow mods such as sheathed weapons to not have to rely on existing body parts and dequip items like a shirt to work. I think this is a bit more complicated to implement due to requiring both in game and open mw cs work to do.

While I would also love to have themed music for different areas, the problem there would be having to mark every cell that uses it, both in vanilla and mods. Also, since towns are outdoors and don't always match up perfectly with grid spaces in the outdoor world, there would have to be a better way to detect the area needed to use town music. Though it would take a lot of work, I could still see it being done, and would be even better if the music could cross-fade.

The way Skyrim handles it, it has manually-defined playlists (so instead of "Explore" being everything in the "Explore" directory, it's defined in the esm/p and has a list of individual songs), and a list of conditions for when each playlist should play (not too unlike Oblivion's AI package handling; run through a series of checks for an entry, and if it passes use it, else go to the next and check that one, etc).

While I would also love to have themed music for different areas, the problem there would be having to mark every cell that uses it, both in vanilla and mods. Also, since towns are outdoors and don't always match up perfectly with grid spaces in the outdoor world, there would have to be a better way to detect the area needed to use town music. Though it would take a lot of work, I could still see it being done, and would be even better if the music could cross-fade.

I would say just marking the cells would work fine.
Some repetitive work for the person who wants to add it in the mod or game.
And while the towns/cities don't always match up with the cells, I don't see many towns/cities where the cell would be outside what I would say is the "town/city area".

Occlusion Plane Support - While I think boundary boxes would take a lot of work, I think an occlusion plane that could be dropped in the OpenMW CS make help in densely populated areas where effectively objects behind it in view of the player would not be rendered. When I play Tamriel Rebuilt and visit Old Ebonheart it makes me think that this would be an area where it would be beneficial.

I was just going to post about something like this. There is the Janua occlusion culling engine that could be used to pregenerate occlusion culling data for use in-game, to increase performance in cities and other places with a lot of objects. Manually placing occlusion planes wouldn't be needed with this. I also wonder if it could be used to improve performance of distant terrain and statics.

For Music, I think it could be filtered in much the same way Dialogue is. First by region, and then also be the start of a name of the cell up to and not including the first comma (I.e. Vivec, Foreign Quarter would have the same filter as Vivec)

I would love occlusion culling, especially if we could hook it up to the automatic near/far plane computation so occluded stuff didn't count towards the far plane distance, and even more if there was an occlusion plane under the ground.